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/*
* $Id: libnet_build_dns.c,v 1.10 2004/04/13 17:32:28 mike Exp $
*
* libnet
* libnet_build_dns.c - DNS packet assembler
*
* Copyright (c) 1998 - 2004 Mike D. Schiffman <mike@infonexus.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*/
#include "common.h"
libnet_ptag_t
libnet_build_dnsv4(uint16_t h_len, uint16_t id, uint16_t flags,
uint16_t num_q, uint16_t num_anws_rr, uint16_t num_auth_rr,
uint16_t num_addi_rr, const uint8_t *payload, uint32_t payload_s,
libnet_t *l, libnet_ptag_t ptag)
{
uint32_t n, h;
uint32_t offset;
libnet_pblock_t *p;
struct libnet_dnsv4_hdr dns_hdr;
if (l == NULL)
{
return (-1);
}
if (h_len != LIBNET_UDP_DNSV4_H && h_len != LIBNET_TCP_DNSV4_H)
{
snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,
"%s(): invalid header length: %d", __func__, h_len);
return (-1);
}
offset = (h_len == LIBNET_UDP_DNSV4_H ? sizeof(dns_hdr.h_len) : 0);
n = h_len + payload_s;
h = 0; /* no checksum */
/*
* Find the existing protocol block if a ptag is specified, or create
* a new one.
*/
p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_DNSV4_H);
if (p == NULL)
{
return (-1);
}
/*
* The sizeof(dns_hdr.h_len) is not counted is the packet size
* for TCP packet.
* And since this will be ignored for udp packets, let's compute it
* anyway.
*/
memset(&dns_hdr, 0, sizeof(dns_hdr));
dns_hdr.h_len = htons(n - sizeof (dns_hdr.h_len));
dns_hdr.id = htons(id);
dns_hdr.flags = htons(flags);
dns_hdr.num_q = htons(num_q);
dns_hdr.num_answ_rr = htons(num_anws_rr);
dns_hdr.num_auth_rr = htons(num_auth_rr);
dns_hdr.num_addi_rr = htons(num_addi_rr);
/*
* A dirty trick: DNS can be either TCP or UDP based, and depending on
* that, the header changes. A 'length' field is present in TCP packets,
* but not in UDP packets. As they are the first 2 bytes of the header,
* they are skipped if the packet is UDP...
*/
n = libnet_pblock_append(l, p, ((uint8_t *)&dns_hdr) + offset, h_len);
if (n == -1)
{
goto bad;
}
/* boilerplate payload sanity check / append macro */
LIBNET_DO_PAYLOAD(l, p);
return (ptag ? ptag : libnet_pblock_update(l, p, h, LIBNET_PBLOCK_DNSV4_H));
bad:
libnet_pblock_delete(l, p);
return (-1);
}
/* EOF */
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